Trench schottky diodes are known. An example of a trench schottky diode is shown in the copending application Ser. No. 10/193,783, filed Jul. 11, 2002 and assigned to the assignee of the present invention.
The device shown in application Ser. No. 10/193,783 includes an active region that includes a plurality of trenches, and a termination region which includes a termination trench. In the device shown in application Ser. No. 10/193,783 the sidewalls and the bottoms of the trenches in the active region, and the sidewalls and the bottom of the termination trench are lined with an oxide layer, which is formed simultaneously in the trenches of the active region and the termination trench.
The thickness of the oxide layer in the active region is related to the breakdown voltage (BV) of the device. Thus, for an epitaxial silicon of a given resistivity in which trenches are formed, there is an optimum oxide thickness that provides the maximum BV for the trenches. However, the thickness of the oxide in the termination trench mainly affects reverse voltage stability and ruggedness.
Because the thickness of the oxide in the active region and the thickness of the oxide in the termination region are about the same, there is a possibility that the termination will breakdown prior to the active region. This premature breakdown will reduce the overall efficiency of the device.